etcdctl/cluster_health: improve output if failed to get leader stats
etcdctl/cluster_health: improve output if failed to get leader stats

When failing to get leader stats, it said 'cluster is unhealthy' before.
This is confusing when it cannot get stats because advertised client urls
are set wrong and the cluster is healthy.

xebitstudios/etcd,bdarnell/etcd,chipironcin/etcd,improbable-io/etcd,siddontang/etcd,glensc/etcd,xdlinear/etcd,mqliang/etcd,raoofm/etcd,betawaffle/etcd,sebrandon1/etcd,zaphod-concur/etcd,HideoYamauchi/etcd,vimalk78/etcd,axingblog/etcd,steveeJ/etcd,a-robinson/etcd,fasaxc/etcd,xdlinear/etcd,SivagnanamCiena/etcd,yudai/etcd,cockroachdb/etcd,crandles/etcd,sofuture/etcd,TheHippo/etcd,gae123/etcd,purpleidea/etcd,mickep76/etcd,rnaveiras/etcd,jefby/etcd,hroyrh/etcd,xebitstudios/etcd,xiang90/etcd,devfreesg/etcd,fgbreel/etcd,ajityagaty/etcd,csuideal/etcd,svdata/etcd,mitake/etcd,jlamillan/etcd,svdata/etcd,coreos/etcd,jeremyeder/etcd,honeyqa/etcd,bspline/etcd,sayden/etcd,gityf/etcd,akauppi/etcd,cockroachdb/etcd,msanterre/etcd,njucslqq/etcd,xychu/etcd,snailwalker/etcd,asim/etcd,xychu/etcd,delkyd/etcd,wantonsolutions/dinv-etcd,jmptrader/etcd,gtank/etcd,kingland/etcd,qiaochao911/etcd,hongbinz/etcd,insionng/etcd,chipironcin/etcd,sebschrader/etcd,HideoYamauchi/etcd,joshix/etcd,mwitkow/etcd,swingbach/etcd,Eagle-X/etcd,StorReduce/etcd,tempbottle/etcd,shawnps/etcd,junxu/etcd,hzy001/etcd,gae123/etcd,shakefu/etcd,gouyang/etcd,hongbinz/etcd,onlyjob/etcd,mkumatag/etcd,dnaeon/etcd,handsomesun/etcd,jchauncey/etcd,buaazp/etcd,dannysauer/etcd,jmptrader/etcd,glycerine/etcd,chenbaihu/etcd,coreos/etcd,Timer/etcd,nieanan/etcd,heyitsanthony/etcd,cchamplin/etcd,mickep76/etcd,jonboulle/etcd,li-ang/etcd,etcd-io/etcd,cognusion/etcd,yudai/etcd,yyljlyy/etcd,oscarrr110/etcd,bluebreezecf/etcd,sofuture/etcd,endocode/etcd,ravigadde/etcd,visheshnp/etcd,tamird/etcd,combk8s/etcd,vimalk78/etcd,qqsun8819/etcd,beni55/etcd,es-chow/etcd,kingland/etcd,njharman/etcd,hongchaodeng/etcd,visheshnp/etcd,giantswarm/etcd,ravigadde/etcd,dnaeon/etcd,openedbox/etcd,rnaveiras/etcd,pauldallen/etcd,OyTao/etcd_learning,Yhgenomics/etcd,oscarrr110/etcd,fgbreel/etcd,etcd-io/etcd,mwitkow-io/etcd,pengzj/etcd,gyuho/etcd,plasticbox/etcd,achanda/etcd,QuantiumTechnology/etcd,hzy001/etcd,tangkun75/etcd,es-chow/etcd,armstrongli/etcd,kkaneda/etcd,mwitkow/etcd,mitake/etcd,arthurcolle/etcd,ylong/etcd,fanminshi/etcd,jchauncey/etcd,StorReduce/etcd,yifan-gu/etcd,njucslqq/etcd,bluebreezecf/etcd,insequent/etcd,luxas/etcd,jonboulle/etcd,wantonsolutions/dinv-etcd,wowsoso/etcd,nekto0n/etcd,ylong/etcd,tguangch/etcd,cchamplin/etcd,shafreeck/etcd,lzbgt/etcd,li-ang/etcd,offscale/etcd,lumjjb/etcd,Timer/etcd,jravetch/etcd,youxidev/etcd,jravetch/etcd,qqsun8819/etcd,csuideal/etcd,mike-lerch/etcd,xueshanf/etcd,YuleiXiao/etcd,Yhgenomics/etcd,hongchaodeng/etcd,imzhulei/etcd,rchicoli/etcd,wfxiang08/etcd,mwitkow-io/etcd,endocode/etcd,mqliang/etcd,polvi/etcd,glensc/etcd,barakmich/etcd,tangkun75/etcd,raoofm/etcd,sinsharat/etcd,rnaveiras/etcd,luxas/etcd,steveeJ/etcd,fasaxc/etcd,insequent/etcd,a-robinson/etcd,improbable-io/etcd,pengzj/etcd,princeqjzh/etcd,mqliang/etcd,freeloop1114/etcd,iamqizhao/etcd,lorneli/etcd,mike-lerch/etcd,imzhulei/etcd,wfxiang08/etcd,whuwxl/etcd,tguangch/etcd,ajityagaty/etcd,yifan-gu/etcd,Winslett/etcd,sebrandon1/etcd,akauppi/etcd,siddontang/etcd,whuwxl/etcd,offscale/etcd,snailwalker/etcd,linuxcer/etcd,shakefu/etcd,bspline/etcd,Winslett/etcd,xueshanf/etcd,giantswarm/etcd,CrazyJvm/etcd,heyitsanthony/etcd,bdarnell/etcd,lzbgt/etcd,tempbottle/etcd,jefby/etcd,arthurcolle/etcd,chenbaihu/etcd,onlyjob/etcd,elimisteve/etcd,qiaochao911/etcd,joshix/etcd,mkumatag/etcd,axingblog/etcd,nkhare/etcd,wantonsolutions/dinv-etcd,beni55/etcd,mkumatag/etcd,junxu/etcd,achanda/etcd,freeloop1114/etcd,gyuho/etcd,westhood/etcd,ktateish/etcd,etcd-io/etcd,fanminshi/etcd,gtank/etcd,combk8s/etcd,westhood/etcd,betawaffle/etcd,TheHippo/etcd,armstrongli/etcd,barakmich/etcd,yyljlyy/etcd,zaphod-concur/etcd,pauldallen/etcd,sinsharat/etcd,OyTao/etcd_learning,glevand/coreos--etcd,wowsoso/etcd,hroyrh/etcd,honeyqa/etcd,jeremyeder/etcd,yichengq/etcd,dalanlan/etcd,ktateish/etcd,xiang90/etcd,njharman/etcd,msanterre/etcd,gityf/etcd,delkyd/etcd,jlamillan/etcd,dalanlan/etcd,Eagle-X/etcd,nieanan/etcd,kkaneda/etcd,olark/etcd,lorneli/etcd,openedbox/etcd,cognusion/etcd,iamqizhao/etcd,shafreeck/etcd,nekto0n/etcd,purpleidea/etcd,olark/etcd,youxidev/etcd,tamird/etcd,SivagnanamCiena/etcd,plasticbox/etcd,ajityagaty/etcd,buaazp/etcd,crandles/etcd,dannysauer/etcd,linuxcer/etcd,sayden/etcd,QuantiumTechnology/etcd,yichengq/etcd,handsomesun/etcd,asim/etcd,lumjjb/etcd,gouyang/etcd,YuleiXiao/etcd,CrazyJvm/etcd,glycerine/etcd,nkhare/etcd,glevand/coreos--etcd,swingbach/etcd,fasaxc/etcd,sebschrader/etcd,elimisteve/etcd,polvi/etcd,spacejam/etcd,rchicoli/etcd,shawnps/etcd,devfreesg/etcd,spacejam/etcd,insionng/etcd,princeqjzh/etcd